### Abstract

Using a box profile approximation for the non-electrostatic surface adsorption potentials of anions and cations, we calculate the differential capacitance of aqueous electrolyte interfaces from a numerical solution of the Poisson-Boltzmann equation, including steric interactions between the ions and an inhomogeneous dielectric profile. Preferential adsorption of the positive (negative) ion shifts the minimum of the differential capacitance to positive (negative) surface potential values. The trends are similar for the potential of zero charge; however, the potential of zero charge does not correspond to the minimum of the differential capacitance in the case of asymmetric ion adsorption, contrary to the assumption commonly used to determine the potential of zero charge. Our model can be used to obtain more accurate estimates of ion adsorption properties from differential capacitance or electrocapillary measurements. Asymmetric ion adsorption also affects the relative heights of the characteristic maxima in the differential capacitance curves as a function of the surface potential, but even for strong adsorption potentials the effect is small, making it difficult to reliably determine the adsorption properties from the peak heights.

Original language | English |
---|---|

Article number | 064002 |

Journal | Journal of Physics Condensed Matter |

Volume | 30 |

Issue number | 6 |

DOIs | |

Publication status | Published - 17 Jan 2018 |

Externally published | Yes |

### Fingerprint

### Keywords

- capacitance
- electrolyte solution
- ion adsorption

### ASJC Scopus subject areas

- Materials Science(all)
- Condensed Matter Physics

### Cite this

**The effects of ion adsorption on the potential of zero charge and the differential capacitance of charged aqueous interfaces.** / Uematsu, Yuki; Netz, Roland R.; Bonthuis, Douwe Jan.

Research output: Contribution to journal › Article › Research › peer-review

*Journal of Physics Condensed Matter*, vol. 30, no. 6, 064002. https://doi.org/10.1088/1361-648X/aaa4d4

}

TY - JOUR

T1 - The effects of ion adsorption on the potential of zero charge and the differential capacitance of charged aqueous interfaces

AU - Uematsu, Yuki

AU - Netz, Roland R.

AU - Bonthuis, Douwe Jan

PY - 2018/1/17

Y1 - 2018/1/17

N2 - Using a box profile approximation for the non-electrostatic surface adsorption potentials of anions and cations, we calculate the differential capacitance of aqueous electrolyte interfaces from a numerical solution of the Poisson-Boltzmann equation, including steric interactions between the ions and an inhomogeneous dielectric profile. Preferential adsorption of the positive (negative) ion shifts the minimum of the differential capacitance to positive (negative) surface potential values. The trends are similar for the potential of zero charge; however, the potential of zero charge does not correspond to the minimum of the differential capacitance in the case of asymmetric ion adsorption, contrary to the assumption commonly used to determine the potential of zero charge. Our model can be used to obtain more accurate estimates of ion adsorption properties from differential capacitance or electrocapillary measurements. Asymmetric ion adsorption also affects the relative heights of the characteristic maxima in the differential capacitance curves as a function of the surface potential, but even for strong adsorption potentials the effect is small, making it difficult to reliably determine the adsorption properties from the peak heights.

AB - Using a box profile approximation for the non-electrostatic surface adsorption potentials of anions and cations, we calculate the differential capacitance of aqueous electrolyte interfaces from a numerical solution of the Poisson-Boltzmann equation, including steric interactions between the ions and an inhomogeneous dielectric profile. Preferential adsorption of the positive (negative) ion shifts the minimum of the differential capacitance to positive (negative) surface potential values. The trends are similar for the potential of zero charge; however, the potential of zero charge does not correspond to the minimum of the differential capacitance in the case of asymmetric ion adsorption, contrary to the assumption commonly used to determine the potential of zero charge. Our model can be used to obtain more accurate estimates of ion adsorption properties from differential capacitance or electrocapillary measurements. Asymmetric ion adsorption also affects the relative heights of the characteristic maxima in the differential capacitance curves as a function of the surface potential, but even for strong adsorption potentials the effect is small, making it difficult to reliably determine the adsorption properties from the peak heights.

KW - capacitance

KW - electrolyte solution

KW - ion adsorption

UR - http://www.scopus.com/inward/record.url?scp=85040936457&partnerID=8YFLogxK

U2 - 10.1088/1361-648X/aaa4d4

DO - 10.1088/1361-648X/aaa4d4

M3 - Article

VL - 30

JO - Journal of physics / Condensed matter

JF - Journal of physics / Condensed matter

SN - 0953-8984

IS - 6

M1 - 064002

ER -